Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, and broadcast services. These wireless communication networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Examples of such multiple-access networks include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.
A wireless communication network may include a number of eNodeBs that can support communication for a number of user equipments (UEs). A UE may communicate with an eNodeB via the downlink and uplink. The downlink (or forward link) refers to the communication link from the eNodeB to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the eNodeB.
As wireless communication technology advances, a growing number of different radio access technologies are being utilized. For instance, many geographic areas are now served by multiple wireless communication systems, each of which can utilize one or more different radio access technologies (RATs). In order to increase versatility of UEs in such systems, there recently has been an increasing trend toward multi-mode UEs that are able to operate in networks using multiple different types of RATs. For example, a multi-mode UE may be able to operate in Global System for Mobile Communications (GSM) or Universal Mobile Telecommunication System (UMTS) systems, as well as long term evolution (LTE) systems.
While allowing a UE to operate across systems with different RATs helps enhance service coverage, switching between such systems may present a challenge, for example, due to different operating requirements.